A 1 liter autoclave was charged with Myriant bio-succinic acid (500 g, 4.2 mol) and methanol (149 g, 4.7 mol, 1.1 equivalent). The vessel was sealed, pressurised to 40 bar(g) under nitrogen and heated to 200° C. at which point the reaction mixture was agitated by stirring at 300 rpm. After 3 hours the vessel was cooled and the product discharged as a light-brown slurry. This process was repeated until sufficient monomethyl succinate had been prepared for further esterification testwork.
The testwork was repeated to obtain discrete samples of monomethyl succinate derived from crude and pure Myriant bio-succinic acid samples.
A 500 ml reaction vessel was charged with 300 g of the crude bio-mono-methyl succinate and 30 g of DPT-2 resin (available from Johnson Matthey Davy Technologies Limited). The vessel was then heated to give an approximate pot temperature of 115° C., with the flange heated to a temperature of 120° C. to reduce internal reflux. Methanol was then introduced directly into the liquor at 3 molar equivalents per hour. The resulting vapour was removed and condensed. Samples of the liquor were taken with time and analysed by titration against 0.1 M potassium hydroxide using phenolphthalein as the indicator and acetone as the solvent. The reaction was continued until the monomethyl succinate concentration was <0.5 wt %.
The experiment was repeated to give 4 runs, the results of which can be seen in FIG. 8. The results of the testwork suggest that there was deactivation of the resin with the crude Myriant succinate.
Analysis of the deactivated resin by XRF indicated the presence of relatively large amounts of Fe, however, this was not seen in the crude bio-monomethyl succinate.